Method of removing wax from cellulosic fiber used in a fiber suspension for a paper-making machine

Abstract

The invention comprises, in one form thereof, a method of removing wax from recycled cellulosic fiber. The cellulosic fiber is pulped in a pulper to a suspension with a consistency of less than about 10% by weight. The suspension is then screened to remove coarse and fine contaminants. The screened suspension is diluted to a consistency of less than about 3% by weight. The wax is removed from the diluted suspension using a froth flotation device. The suspension is then washed and/or thickened.

What is claimed is:  
     
       1. A method of removing wax from recycled cellulosic fiber, comprising the steps of: 
       pulping the cellulosic fiber in a pulper to a suspension with a consistency of less than about 10% by weight;  
       screening the suspension to remove contaminants;  
       diluting the screened suspension to a consistency of less than about 3% by weight, said diluting step including diluting the suspension to a consistency of between about 0.2 and 2.0% by weight;  
       removing wax from the diluted suspension using a froth flotation device, said wax removing step including the substeps of:  
       controlling the pH of the suspension to between about 8.5 and 9.5;  
       controlling an internal temperature of the froth flotation device to between about 85 and 160° F.;  
       introducing air into the suspension at a range of between about 40 and 200% air-to-stock ratio to generate foam which carries wax to the surface of the suspension; and  
       removing the foam with entrained wax therein from the froth flotation device; and  
       adjusting the consistency of the suspension after said wax removing step.  
     
     
       2. The method of claim  1 , wherein said contaminants removed during said screening step are returned to said pulper. 
     
     
       3. The method of claim  1 , wherein the foam is further processed after said foam removing substep. 
     
     
       4. The method of claim  1 , wherein a filtrate is generated in said adjusting step, said filtrate being reused as dilution water for at least one of pulping, screening and flotation. 
     
     
       5. A method of removing wax from recycled cellulosic fiber, comprising the steps of: 
       pulping the cellulosic fiber in a pulper to a suspension with a consistency of less than about 10% by weight, said pulping step comprising the substeps of:  
       diluting the cellulosic fiber to a consistency of between about 4 and 8% by weight;  
       adjusting the pH of the suspension to between about 9.5 and 10.5;  
       adjusting an internal temperature of the pulper to between about 50 and 70 deg C.; and  
       processing the suspension for a time period of between about 20 and 50 minutes in said pulper;  
       screening the suspension to remove contaminants;  
       diluting the screened suspension to a consistency of less than about 3% by weight, said diluting step including diluting the suspension to a consistency of between about 0.2 and 2.0% by weight;  
       removing wax from the diluted suspension using a froth flotation device, said wax removing step including the substeps of:  
       adjusting the pH of the suspension to between about 8.5 and 9.5;  
       adjusting an internal temperature of the froth flotation device to between about 85 and 160 deg F.;  
       introducing air into the suspension at a range of between about 40 and 200% air-to-stock ratio to generate foam which carries wax to the surface of the suspension; and  
       removing the foam with entrained wax from the froth flotation device; and further processing the suspension using at least one of a thickener and washer.  
     
     
       6. The method of claim  5 , wherein sodium hydroxide is added to the froth flotation device.